Within the construction industry, it is often necessary to accurately align a first position on a support surface with a vertically displaced second position. This is often accomplished by a device commonly referred to as a "plumb bob". A plumb bob generally consists of a flexible string with a weighted marker at one end. In use, the free end of the string is placed at a second position and the weighted marker is allowed to hang freely until it is settled. At this point, the marker will be pointing at a first position which is vertically aligned with the second position. This result occurs after a trial and error procedure. That is, the alignment operation concludes only after constantly moving the upper string at the second position until it ultimately points at the first position. The instant invention provides an apparatus for vertically aligning two positions without the repeated trial and error required by the earlier "plumb bob" devices.
Mechanical plumb bobs operate to vertically align two displaced positions. These aligners are presently being replaced by devices utilizing projected light sources.
In U.S Pat. Nos. 4,106,207 and 4,206,550, Boyett et al. there is disclosed point-to-point self plumbing apparatuses. These patents illustrate a process whereby alignment is created by a light source mounted within a gimbal system. The combination results in a device which accurately projects a beam of light along a vertical line. In the two devices of Boyett et al, upper and lower positions are marked by the light source as the beam is directed in two opposite directions.
Similarly, U.S. Pat. Nos. 3,505,739 and 3,911,588, issued to Abrams and Ohneda, respectively, disclose vertical alignment devices utilizing a projected light source. However, in contrast to the patents granted to Boyett et al, these patents disclose upwardly oriented light sources and downwardly directed markers. As with Boyett et al, these devices utilize gimal arrangements to achieve the necessary alignment between the markers and light sources. Gleba (U.S. Pat. No. 3,772,797) discloses an alternate arrangement to the use of a gimbal type balance. Gleba shows the use of pivotally mounted hangers to provide proper alignment in a projected light plumb device.
The patents discussed above illustrate light projected plumb devices. Their mechanical structures result in expensive and complicated devices. They require exacting specifications to produce the proper balance of their components and with these specifications come elaborate methods for utilizing the devices. The instant invention overcomes the problems associated with such mechanical devices by providing a suspension fluid for supporting the light projecting source.
Prier, in U.S. Pat. No. 701,612, discloses the use of fluid in a leveling instruments. Though Prier does disclose a fluid filled trough with a float supported therein, Prier's device is used for leveling and surveying and not for alignment. That is, a user looks through an eyepiece with cross-hairs and lines up the cross-hairs with the plumb-bob rod prior to using the device as a surveying transit. In contrast, the instant invention includes the combination of a light projecting device and a suspension fluid to vertically align a first position on a support surface with a corresponding second position on a second surface.